1. Field of the Invention
This invention is concerned with a pentaerythritol ester base lubricating oil composition for a gas turbine engine. Gas turbine engines are operated under a wide range of temperature conditions. The lubricant must be fluid at extremely low temperatures and at the same time retain its lubricating properties in an engine which produces internal operating temperatures of 450-550.degree. F. or above. The lubricant is subjected to severe oxidation stresses under the high running temperatures encountered in such engines.
Ester base lubricating oil compositions prepared from pentaerythritol and a mixture of fatty acids containing selective additive combinations are well known. These lubricants are functional over a wide temperature range and exhibit good thermal and oxidative stability. The search for a still more effective, long lived ester base lubricant composition, however, is a major goal of lubricant manufacturers. In addition, more advanced gas turbine engines currently being developed and tested will put higher stresses on the lubricant composition and are projected to require improved lubricant compositions.
2. DESCRIPTION OF THE PRIOR ART
U.S. Pat. No. 3,719,126 discloses a lubricating oil composition which is non-corrosive to silver and silver alloys containing an oil-soluble polysulfide derivative of 2,5-dimercapto-1,3,4-thiadiazole.
U.S. Pat. No. 3,756,952 discloses an ester base lubricating oil composition containing an ammonium thiocyanate in combination with a polyhydroxy-substituted anthraquinone.
U.S. Pat. No. 3,247,111 discloses an ester base lubricating oil composition containing phenyl-naphylamine, dioctyldiphenylamine and quinizarin.
British Pat. No. 1,180,387 discloses an ester base lubricating oil composition containing an alkylated diphenylamine, alkylated phenyl naphthylamine and a neutral organic phosphate.